Rotary roller pumps

ABSTRACT

A rotary roller pump comprising a cylindrical pump chamber closed at both ends and having inlet and outlet openings into the chamber, a rotor eccentrically mounted in the pump chamber on a cantilever shaft, and a plurality of rollers located in longitudinal slots in the periphery of the rotor; the entire rotor is of molded plastic, keyed to the shaft. The periphery of the rotor, between roller slots, comprises a series of voids with central reinforcing ribs; apertures through the ribs equalize pressures on opposite sides of the rotor.

Burenga et al.

[ 1 May 22, 1973 [54] ROTARY ROLLER PUMPS [75] Inventors: Thomas I. Burenga, Evanston, Ill.; Everett Elliott, Richland Center, Wis.

[73] Assignee: TSC Industries Inc., Chicago, Ill.

[22] Filed: Mar. 29, 1971 [21] Appl. No.: 128,916

[52] US. Cl ..418/152, 418/225 [51] Int. Cl ..F01c 21/00, F03c 3/00, F04c 15/00 [58] Field of Search ..4l8/152, 179, 225-227, 418/153 [56] References Cited UNITED STATES PATENTS 3,207,079 9/1965 Cook et a1. ..418/225 1 2,455,194 11/1948 Rumsey.... .....418/154 3,381,622 5/1968 Wilcox ..4l8/225 1,265,070 5/1918 Feyzes ..4l8/225 FOREIGN PATENTS OR APPLICATIONS 614,712 6/1961 Italy AIS/225 Primary Examiner-Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney-Kinzer, Dom & Zickert [57] ABSTRACT A rotary roller pump comprising a cylindrical pump chamber closed at both ends and having inlet and outlet openings into the chamber, a rotor eccentrically mounted in the pump chamber on a cantilever shaft, and a plurality of rollers located in longitudinal slots in the periphery of the rotor; the entire rotor is of molded plastic, keyed to the shaft. The periphery of the rotor, between roller slots, comprises a series of voids with central reinforcing ribs; apertures through the ribs equalize pressures on opposite sides of the rotor.

5 Claims, 6 Drawing Figures PATENTED W22 I975 SHEET 1 [IF 3 //VVE/VTOR$. THOMAS I. SURE/VGA EVERETT ELL/077 FEE-{LE1 PATENTEB W22 I975 3. 734.654

INVENTORS.

THOMAS I. BURENGA EVERETT ELLIOTT BYKMW 7355/5.

PAIENIEWW 3.734.654

SHEET 3 UF 3 N VE N T 0R5 THOMAS E. BURENGA EVERETT ELLIOTT ROTARY ROLLER PUMPS BACKGROUND OF THE INVENTION Rotary roller pumps are well known in the art; they afford effective and efficient pumps suitable for a wide variety of applications, including the pumping of liquids in industrial plants and in other quite different environments such as agricultural applications. One particularly effective and efficient construction for a pump of this kind is described and claimed in U.S. Pat. No. 3,373,693 to G.D. McKittrick issued Mar. 19, 1968.

A number of difficulties and problems occur in the manufacture and use of rotary roller pumps. A familiar problem, encountered in many different kinds of pumps, related to corrosion of the working members of the pump when the liquid being pumped is itself corrosive or contains corrosive materials in solution or suspension. In the rotary roller pump, this problem has previously been solved by the use of corrosion-resistant alloys in the fabrication of the pump parts, particularly the rotor and the rollers, but this expedient adds substantially to the cost of the pump. Another problem with rotary roller pumps arises when the pump is run dry for any period of time. Conventional rotary roller pumps tend to overheat and to seize up quite rapidly if run without an adequate supply of liquid, to the extent that dry operation for even a few minutes may cause irreparable damage to the pump.

Most rotary pumps have utilized a shaft that extends through the complete pump housing structure, both ends of the shaft being supported in bearings mounted in the pump housing. This makes the pumps difficult to assemble. It also creates substantial problems when field service is necessary, both in stripping the pump down and in re-assembling it. Moreover, although not excessively heavy compared to other competitive types of pumps, the rotary roller pumps of the prior art are nevertheless quite heavy, leading to undesirable costs in manufacture and in shipping.

SUMMARY OF THE INVENTION It is a principal object of the present invention, therefore, to provide a new and improved rotary roller pump that effectively and inherently eliminates or minimizes the problems and difficulties relating to prior art pumps of this type as discussed above.

A specific object of the invention is to provide a new and improved rotor assembly for a rotary roller pump that is inherently corrosion-resistant and that is substantially lighter in weight than the constructions employed in previously known pumps.

A further object of the invention is to provide a new and improved rotor assembly for a rotary roller pump that permits dry operation of the pump for substantial periods without damaging the pump.

A particular object of the invention is to provide a new and improved rotor assembly for a rotary roller pump that combines the use of a cantilever pump shaft with a single support bearing, thereby simplifying the manufacture and field servicing of the pump.

A related object of the invention is to provide a new and improved roller assembly for a rotary roller pump that materially reduces the cost of manufacture and other costs connected with the pump, in comparison with previously known constructions.

Accordingly, the invention relates to a rotor assembly for a rotary roller pump for liquids; the pump comprises a housing defining a cylindrical pump chamber closed at both ends and having inlet and outlet openings through the housing into the pump chamber, with at least one shaft-receiving opening extending through one end of the housing. The rotor assembly comprises a rotor shaft projecting through the shaft-receiving opening of the housing and across the pump chamber; preferably, a cantilever shaft having a single support bearing is utilized. A rotor of molded plastic material is affixed to the shaft and spans the pump chamber from end-to-end, the periphery of the rotor having a plurality of longitudinal roller-receiving slots molded therein. Preferably, the rotor is molded of a glass-filled plastic material with voids between the roller slots and with reinforcing ribs across the voids that are provided with pressure-relieving transverse openings. A corresponding plurality of rollers are individually mounted in the slots, each roller extending from one end of the pump chamber to the other.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of a rotary roller pump constructed in accordance with a preferred embodiment of the present invention;

FIG. 2 is a sectional elevation view taken approximately along line 22 in FIG. 1;

FIG. 3 is a sectional elevation view taken approximately along line 3-3 in FIG. 1;

FIG. 4 is a transverse sectional view taken approximately as indicated by line 4-4 in FIG. 2;

FIG. 5 is an elevation view of the rotor of the pump; and

FIG. 6 is a sectional elevation view of the rotor.

DESCRIPTION OF THE PREFERRED EMBODIMENT The rotary roller pump 10 illustrated in FIGS. 1-4, which comprises a preferred embodiment of the present invention, includes a cylindrical steel sleeve 11 of circular cross-sectional configuration; an inlet plate 12 is mounted on one end of the sleeve 11 and an outlet plate 14 is mounted on the opposite end of the sleeve. As shown in FIG. 2, sleeve 11 fits into an annular groove 13 in the inlet plate 12; a ring gasket may be employed to seal the periphery of sleeve 11 into groove 13. Similarly, the sleeve 11 fits into an annular groove 15 in the outlet plate 14 and may be sealed thereto by an appropriate annular gasket. The pump housing comprising sleeve 11 and inlet plates 12 and 14 is held together by four retainer bolts 16, each bolt extending through both of the end plates 12 and 14.

Inlet plate 12', which may be formed of cast iron or other suitable material, includes a boss 17 through which an inlet opening 18 extends into the pump chamber 19 enclosed by sleeve 11 and end plates 12 and 14. The inlet opening 18 terminates, at the inner surface of inlet plate 12, in two arcuate inlet grooves 21 and 22. The outlet plate 14 of pump 10, which may also be a cast iron member, comprises a boss 23 through which an outlet opening 24 extends. As shown in FIGS. 3 and 4, the outlet opening 24 terminates, at the interior surface of the outlet plate 14 facing the pump chamber 19, in a pair of arcuate outlet slots 25 and 26.

The key features of the present invention are embodied in the rotor assembly 30 mounted in pump chamber 19 of pump 10. Rotor assembly 30 comprises a rotor. shaft 31, preferably formed of stainless steel or other corrosion-resistant metal. Shaft 31 extends into pump chamber 19 through a shaft-receiving opening 27 in the outlet plate 14, projecting almost completely across pump chamber 11. The outer portion of the shaftreceiving opening 27 comprises a bearing cavity in which a single roller bearing 32 is mounted, supporting the outboard end of shaft 31. Inwardly of bearing 32, in a portion of the shaft-receiving opening of slightly reduced diameter, a seal 33 is mounted. A pressure relief passage 34 is provided from the inner end of seal 33 to an arcuate groove 35 facing into pump chamber 11 (see FIGS. 3 and 4).

A rotor 36 of molded plastic material is affixed to the inner end of shaft 33, being disposed within and spanning pump chamber 19 from end-to-end of the pump chamber. The molded plastic rotor 36 is formed from a material that is not substantially affected by and does not absorb the liquid being pumped. For most applications, including water pumping applications in which some relatively corrosive materials may be suspended or dissolved, a 25 percent glass-filled plasticized ethyl cellulose material, commercially available under the trade name Ceicon," has been found to be satisfactory. Other materials suitable for general purpose pumping, including water, are the acetal thermoplastic resin commercially available under the trade name Delrin, and the same resin with a substantial glass filling for additional strength. For many applications, the plastic material from which rotor 36 is molded may be nylon or glass-filled nylon; however, nylon is not desirable for pumping of water or aqueous solutions because it tends to absorb the water and to swell up, ultimately leading to failure of the pump.

The plastic rotor 36 may be molded as a separate member and subsequently mounted on shaft 31. Preferably, however, the shaft is present in the mold at the time the rotor is formed, so that the rotor is molded in situ on the shaft. This allows close control of the concentricity of the shaft and rotor and gives the best overall results with respect to maintenance of close tolerances, as is highly desirable in the fabrication of a pump of this kind.

It is necessary to provide an effective driving interlock between shaft 31 and the molded plastic rotor 36. In the preferred construction, shaft 31 is provided with a plurality of integral interlock elements comprising the squeezed metal tabs 37 and the adjacent indentations 38 formed when the tabs 37 are pinched from the metal shaft. The plastic rotor 36 fits over the interlock elements, and into the interlock elements to the extent that the interlock elements comprise indentations, and firmly locks the rotor on the shaft. The integrity of the interlock construction is assured in those pumps in which the plastic rotor 36 is molded in situ on the shaft 31 and this type of construction affords the best possible interlock arrangement.

As noted above, rotor 36 extends from end to end of pump chamber 19. Close tolerance should be maintained in fabrication of the rotor to assure a good seal against the planar faces of the end plates 12 and 14 in the interior of chamber 19. Because the plastic material from which rotor 36 is formed constitutes a relatively good bearing material, the rotor is preferably extended over the end of shaft 31 so that only the rotor plastic engages the internal surface of the inlet plate 12.

As shown in FIG. 2, rotor 36 has a plurality of rollerreceiving slots 41 around its periphery. Each of the slots 41 extends longitudinally through the complete length of the rotor, as shown in FIGS. 4 and 5. A corresponding plurality of rollers 42 are incorporated in the rotor assembly 30, one roller 42 in each slot 41 (see FIG. 2). Preferably, rollers 42 are formed of plastic, or constitute plastic-coated metal rollers, so that they have the same basic corrosion-resistant characteristics as rotor 36.

In conventional rotors for rotary roller pumps, the peripheral portions of the rotors, between adjacent roller slots, are solid, with uninterrupted external arcuate surfaces. In rotor 36, however, this practice is not followed. Thus, the spaces between adjacent roller slots 41 around the periphery of rotor 36 constitute a series of voids 44. That is, there is a substantial void 44 between each adjacent pair of roller slots 41. The wall at each side of each roller slot 41 is extended to the full diameter of rotor 36, but most of the intervening space is empty, affording the V-shaped voids 44.

The voids 44 could extend for the full length of the rotor 36; however, this construction is not usually strong enough. Consequently, rotor 36 is formed with a series of arcuate reinforcing ribs 45, one of the reinforcing ribs 45 spanning each of the voids 44. This affords the necessary rigidity for the rotor structure, so that the voids 44 do not unduly weaken it. The base of each rib 45 is provided with a transverse aperture 46. The apertures 46 afford an effective means for equalizing pressure, in a longitudinal direction, across the voids 44. The illustrated construction, with the voids 44, the reinforcing ribs 45, and the pressure-equalizing apertures 46, reduces the amount of plastic required for the rotor 36, with some reduction in the rotor weight. The provision of the apertures 46, in particular, assures a quiet-running pump, much quieter than can be obtained otherwise.

As will be apparent from FIG. 2, rotor 36 is disposed eccentrically within pump chamber 19. When the pump is in operation, the rollers 42 move outwardly of their slots 41, by centrifugal force, riding around the interior surface of sleeve 19. The basic pumping action is essentially similar to other rotary roller pumps and need not be described herein.

Because of the reduction in weight of rotor 36, as compared with a conventional cast metal rotor, and because the rotor is formed of a bearing-type material, a cantilever construction for the rotor assembly 30 is practical and effective. This permits elimination of any support bearing in the one end of the pump, comprising inlet plate 12, reducing the cost and weight of the pump in this regard. Furthermore, a single-row ball bearing, such as bearing 32, affords adequate support for the rotor assembly 30. With close tolerance machining, and particularly where a truly circular sleeve 19 affords the main element of the pump chamber housing, the rotor itself provides the second bearing for the rotor assembly. Because there is no bearing on the one end of the shaft, the pump 10 is much easier to assemble, to disassemble, and to service than most conventional pumps.

As pointed out above, the use of a molded plastic material in the fabrication of rotor 36 results in a pump that is much lighter in weight, easier to handle, and easier and less expensive to ship than conventional metalrotor pumps. A major part of the weight reduction, in addition to the differential between the weight of the plastic rotor and that of a metal rotor, results from the elimination of the second shaft bearing and second shaft seal required in a conventional pump. The pump rotor assembly is inherently corrosion-resistant and is entirely rust-proof, alleviating some of the past problems of rotary roller pumps without the expense entailed in the use of corrosion-resistant alloys for the main body of the rotor.

The cost of pump 10, as compared with most conventional pumps, is substantially reduced. There is less machining, there is only one bearing, there is only one seal, and there is a shorter shaft, all contributing to cost reduction. The plastic rotor 36 is cheaper than a cast metal rotor, particularly if a corrosion-resistant metal is considered. The end plate castings, and particularly the inlet plate 12, are simpler and less expensive to manufacture. The pump is easier and faster to assemble and less expensive to ship. I

Pump also affords an important operating advantage. Conventional rotary roller pumps overheat and seize up, leading to irreparable damage, if run dry for short periods of the order of 2 to 5 minutes. Pumps having the construction exemplified by pump 10 have been run dry for periods of over 30 minutes without noticeable damage and without seizing up. This is extremely important in applications where the pump may be used by unskilled personnel, such as in agricultural pumping operations. In addition, pump 10 can be run at a higher speed for longer periods of time than otherwise compa rable pumps using metal rotors.

It will be recognized that the details of pump 10 can be changed without departure from the true spirit and scope of the invention. For example, the inlet and outlet openings can both be located in one end plate for the pump, instead of in separate end plates as in the illustrated construction. The stator sleeve can be cast integrally with one of the end plates and can include either one or both of the inlet and outlet exterior connections if desired; however, the simple cylindrical sleeve construction shown in the drawings is preferred.

We claim:

1. A rotor assembly for a rotary roller liquid pump, of the kind comprising a housing defining a cylindrical pump chamber closed at both ends and having an inlet opening through said housing into said pump chamber, an outlet opening through said housing into said pump chamber, and at least one shaft-receiving opening extending through one end of said housing, said rotor assembly comprising:

a rotor shaft projecting through said shaft-receiving opening and across said pump chamber;

a rotor of molded plastic material affixed to said shaft and spanning said pump chamber from end to end, the periphery of said rotor having a plurality of Iongitudinal roller-receiving slots molded therein;

the periphery of said rotor having a corresponding plurality of voids formed thereon, in the segments of the rotor intermediate said roller-receiving slots, each void extending from a full-diameter wall at one roller slot to a full-diameter wall at the next adjacent roller slot;

said rotor further comprising a corresponding plurality of arcuate reinforcing ribs, each spanning a medial portion of one of said voids to brace the walls thereof;

and a corresponding plurality of rollers each mounted in one of said slots and extending from one end of said pump chamber to the other.

2. A rotor assembly for a rotary roller pump according to claim 1, in which said shaft includes a plurality of integral interlock elements and in which said rotor is molded in situ on said shaft, in complementary configuration with said interlock elements, said interlock elements each comprising both a recess in said shaft and a projection from said shaft, affording a positive rotary driving connection between said rotor and said shaft and preventing axial displacement of said rotor along said shaft.

3. A rotor assembly for a rotary roller pump according to claim 1, in which each said reinforcing rib has an aperture through the base of the rib to equalize pressure on the opposite sides of the rib.

4. A rotor assembly for a rotary roller pump according to claim 1, in which said rotor is formed of a plastic material selected from the group consisting of thermoplastic acetal resin and plasticized ethyl cellulose, and in which the plastic material is filled with glass fiber.

5. A rotor assembly for a rotary roller pump according to claim 1, in which said rotor is molded in situ on said shaft and is formed of glass-filled plasticized ethyl cellulose. 

1. A rotor assembly for a rotary roller liquid pump, of the kind comprising a housing defining a cylindrical pump chamber closed at both ends and having an inlet opening through said housing into said pump chamber, an outlet opening through said housing into said pump chamber, and at least one shaft-receiving opening extending through one end of said housing, said rotor assembly comprising: a rotor shaft projecting through said shaft-receiving opening and across said pump chamber; a rotor of molded plastic material affixed to said shaft and spanning said pump chamber from end to end, the periphery of said rotor having a plurality of longitudinal roller-receiving slots molded therein; the periphery of said rotor having a corresponding plurality of voids formed thereon, in the segments of the rotor intermediate said roller-receiving slots, each void extending from a fulldiameter wall at one roller slot to a full-diameter wall at the next adjacent roller slot; said rotor further comprising a corresponding plurality of arcuate reinforcing ribs, each spanning a medial portion of one of said voids to brace the walls thereof; and a corresponding plurality of rollers each mounted in one of said slots and extending from one end of said pump chamber to the other.
 2. A rotor assembly for a rotary roller pump according to claim 1, in which said shaft includes a plurality of integral interlock elements and in which said rotor is molded in situ on said shaft, in complementary configuration with said interlock elements, said interlock elements each comprising both a recess in said shaft and a projection from said shaft, affording a positive rotary driving connection between said rotor and said shaft and preventing axial displacement of said rotor along said shaft.
 3. A rotor assembly for a rotary roller pump according to claim 1, in which each said reinforcing rib has an aperture through the base of the rib to equalize pressure on the opposite sides of the rib.
 4. A rotor assembly for a rotary roller pump according to claim 1, in which said rotor is formed of a plastic material selected from the group consisting of thermoplastic acetal resin and plasticized ethyl cellulose, and in which the plastic material is filled with glass fiber.
 5. A rotor assembly for a rotary roller pump according to claim 1, in which said rotor is molded in situ on said shaft and is formed of glass-filled plasticized ethyl cellulose. 